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The crew of German U-boat UC-12, is sent on a standard mission; penetrate the North Sea defensive zone, make their way to Tyneside, lay their mines and return. But nothing in the Great War is that simple. While underwater, the crew start to hear a strange, muffled booming noise, ringing like a sequence of church bells. It's not whales. It's not enemy forces. Something else is down here. While settled on the sea floor to get some much-needed rest, the crew starts to act suspiciously. Someone is up to no good. The ship's cat disappears and a strange weed is found growing on board.
Then the tapping on the hull begins.
Then the tapping on the hull begins.
